Asymmetric impact of a 3D vortex ring on finite-width flexible plate at low Reynolds numbers

A numerical investigation of a vortex ring impinging asymmetrically on a finite-width flexible plate at Re=500, 1500, 2500 is conducted. Results reveal that 3D vortex dynamics significantly influence the plate’s energy harvesting efficiency. At Re=500, high viscosity inhibits the secondary vortices formation at the plate edges/upper wall and enhances primary vortex ring (PVR) stability, resulting in a smooth load decrease. In contrast, Re=1500 and 2500 generate substantial secondary vortices. Under the PVR’s induction, these secondary vortices lift and entangle in PVR, inducing high compression and torsional of PVR vortex tube, which leads to its energy dissipation. Notably, at Re=2500, high turbulence instability promotes stronger secondary vortices, resulting in significant impact energy loss of PVR. Concurrently, these vortices coupling also enhances PVR deformation and vortex shedding, impeding energy transfer to the plate. This interaction results in a smaller increment in energy harvesting efficiency from Re=1500 to Re=2500. Our analysis reveals that the flexible plate’s harvesting efficiencies don’t increase monotonically with the Reynolds number. Instead, the energy harvesting efficiency tends to saturate around Re=1500. This phenomenon is governed by the interplay of 3D vortex evolution, coupling effects, viscous dissipation, and turbulent diffusion, with potential implications for ocean vortex energy harvesting devices optimizations.